O-methyl-N-nitroisourea is represented by the following chemical formula (1).

O-methyl-N-nitroisourea is useful, for example, as a synthetic intermediate of guanidine derivatives which are useful as an insecticide.
As a process for producing O-methyl-N-nitroisourea, there has been a known process for reacting O-methylisourea with nitrating agents.
In the process, after the nitration is performed with nitric acid in sulfuric acid, the reaction mixture is poured into cold water, or ice, or ice water, and cooled to about −15 degree centigrade. When the generated O-methyl-N-nitroisourea is collected by filtration, O-methyl-N-nitroisourea is obtained in only about 75% yield by filtration (for example, refer to Non-patent Document 1). Because O-methyl-N-nitroisourea is water soluble.
Furthermore, by extracting O-methyl-N-nitroisourea from a filtrate after filtration, the yield is increased to about 90%. However, since the solubility of O-methyl-N-nitroisourea to a solvent which can be used for extraction is not so high, large amount of organic solvent is needed for the extraction and the procedure becomes complicated. Thus, the process is not industrially advantageous (for example, refer to Patent Document 2, Non-patent Documents 1 and 2).
Further, since effective isolation and purification of N-nitroisourea are difficult, N-nitroisourea is used for the next reaction without isolation (refer to Patent Document 1).
Patent Document 1: WO01/42787
Patent Document 2: WO97/00867
Non-patent Document 1: Recueil des Travaux Chimiques des Pays-Bas, Vol. 81, p. 69 (1962)
Non-patent Document 2: Journal of Chemical Society, p. 3551 (1955)